A technique of computer color matching (abbreviated to CCM) is developed and practically used as a method for identifying a color material contained in a paint color whose composition is unknown.
However, the present CCM is a method for estimating a pain-color pigment made of only a solid pigment excluding a flaky brilliant material (aluminum flake, mica flake, or plate-like iron oxide) in accordance with spectral reflectance data, which has used a method obtained by combining Kubelka-Munks' two-luminous-flux theory, Duncan's color-mixing theory, and moreover Saunderson's surface-reflectance correction theory since many years ago.
However, CCM of a paint color containing a brilliant material is not practically used at present. This is because additivity is effectuated between lights (reflected light and coherent light) reflected from a brilliant material at highlight of a paint plate (nearby regular reflection light) but absorption of light due to a pigment occurs at the same time. Moreover, this is because coloring occurs due to absorption of light by a brilliant material and pigment in the case of shade (direction opposite to regular reflection light). That is, this is because it is impossible to theorize the coloring characteristic of a color material contained in a paint film in a wide range from highlight up to shade.
Moreover, the number of types of brilliant materials has suddenly increased in recent years. Only in the case of aluminum flake, a product whose surface is covered with an organic pigment, a product from which ion oxide is extracted through CVD, a product which is colored through anode oxidation, a product in which vacuum-deposited aluminum is covered with various metal oxides are developed one after another and a color material in which colors of highlight and shape are changed among brilliant materials is developed. The following are known as brilliant materials: approx. 100 types of aluminum flakes and approx. 300 types of mica flakes and plate-like iron oxides other than aluminum flakes.
When separating from the standpoint of color matching, a method for estimating the composition of a metallic paint color is already present. For example, in the official gazette of Japanese Patent Laid-Open No. (Hei) 7-150081 (TOYOTA), a method is disclosed in which a specified value corresponding to quantities of a color material and a brilliant material constituting a paint color is set, a reflectance decided by a designer is computed in accordance with an already-known reflectance and characteristic-value vector using an inverse estimation method according to interpolation to estimate a composition. In the case of this method, a designer obtains an imaginary color obtained by using an apparatus for computer graphic (CG) as varied-angle reflectance data and estimates a type and quantity in accordance with an already-prepared color-material database so as to match with the reflectance.
Moreover, Japanese Patent Laid-Open No. (Hei) 10-227696 discloses a method for estimating a composition by a “CCM technique” in accordance with the paint-color reflectance data. However, a specific CCM method for a metallic-paint color is not disclosed but only a general method is comprehensively disclosed.
The above two methods respectively estimate a composition by using spectral reflectance data. The spectral reflectance data is means preferable for macroscopic color-scientific measurement of a paint color but it is impossible to measure a microscopic texture containing a brilliant material. In this case, the texture denotes a texture obtained from the grain size and coloring characteristic of a brilliant material and a contained quantity of the brilliant material so that a paint color containing much large-grain-size aluminum provides “glittering” metallic feeling and a paint color containing small-grain-size aluminum provides “silky” metallic feeling. In general, most average grain sizes of brilliant materials used for paints (vehicles, construction, and industries) range between 5 and 200 μm, particularly most average grain sizes of brilliant materials used for final coating of vehicles range between 5 and 30 μm and most thicknesses of them range between 0.1 and 1.0 μm.
It is general that the measuring area of a colorimeter for measuring colors ranges between 5 and 30 mmφ but the colorimeter cannot measure micro glittering feeling.
Therefore, the present solving method is a method in which a skilled color-matching person visually selects various color materials (pigments and brilliant materials), prepare a paint while changing quantities of the color materials, and performs coating by an automatic coating machine, color-matching a macroscopic color and a microscopic texture. Because this method requires a lot of man-hours and depends on a personal ability, it is impossible to estimate and manage the time until color matching is completed.
Moreover, in the field of paint makers, color matching of paint colors whose composition is unknown prepared by a maker other than the company of its own (this is referred to as “color reproduction of other company's color) and problems of the paint colors continuously occur and therefore, development of a color-reproducing technique is a matter of life or death. In this case, the color reproduction includes not only macroscopic coloring from highlight up to shade but also matching of textures due to sizes of brilliant materials from highlight up to shade.